3D molecule model and crystal lattice builder, ready to print
Pick a molecule, a crystal lattice or a formula and see the model in 3D, built from reference bond lengths and angles or by VSEPR (the rule that sets the shape of a molecule). The library models download as STL or 3MF, and the other modes give a curve, a table or a chart.
Part of Pro, 15 EUR a month.
- 14 modesfrom a molecule to a diffraction pattern
- 12 moleculeswith reference lengths and angles
- 8 latticesfrom NaCl to graphite
- STL and 3MFa model to print
3D molecule model: what the tool builds
A 3D molecule model or a crystal lattice is built online by Molecules & Crystals, an EduFacturing tool that is part of Pro: from reference bond lengths and angles, and by VSEPR for a formula. It also calculates the properties that follow from the shape. The library has 12 molecules, 8 crystal lattices and a build from a simple formula.
The other modes are physics on the same geometry: molecular motion, the cell and defects, a diffraction pattern and thermal properties.
Crystal lattice, shape from a formula, diffraction: what it does
Builds a 3D molecule model and a crystal lattice
Twelve molecules, from H₂O and CO₂ to benzene, and eight lattices (NaCl, CsCl, diamond, zinc blende, copper, iron, magnesium, graphite) in a block of 1 to 4 cells per axis. A formula like SF₆ is built by VSEPR; a chain or a ring is refused.
Sets the molecule moving
Dynamics run on a water molecule: velocity Verlet with a thermostat, temperature and vibration spectrum from the motion itself, and a diffusion coefficient. Torsion is for ethane and hydrogen peroxide.
Calculates the crystal cell
Any cell (a, b, c, α, β, γ) with the volume by two methods, Miller planes and directions, defects (vacancies, impurities, a dislocation, a grain boundary) and a powder diffraction pattern for cubic lattices.
Estimates thermal properties and gives a model to print
Thermal expansion, a Lindemann melting temperature accurate to ±30 to 50%, and a teaching hardness index. STL and 3MF download at a chosen scale, checked against the minimum wall.
Molecule models for chemistry lessons and for printing
The shape of a molecule and the arrangement of atoms explain the property a table only names.
A chemistry lesson
A teacher shows why water is bent at 104.45° while CO₂ is straight, and prints both models.
Materials science
A student compares copper, iron and diamond by lattice and by diffraction pattern.
A molecule model to print
Atoms and bonds print at up to 60 mm per ångström, and a lattice fits in a block of cells.
How the molecule is built and where the calculations come from
Every mode is a calculation on a structure of atoms with coordinates in ångströms. The geometry comes from reference lengths and angles or from VSEPR, and the calculations run in the browser.
Geometry
A formula is split into elements, the valence electrons come from the group in the periodic table, and the bond length is the sum of covalent radii, an approximation. For H₂O, NH₃ and SO₂ the angle is measured, otherwise it is the ideal VSEPR angle.
Cell and volume
The volume is calculated by a trigonometric formula and as the scalar triple product of the vectors. The two results must agree to a relative difference below 10⁻⁶.
Motion and energy
Bonds and angles of the water molecule are harmonic, minimisation is steepest descent, and dynamics is velocity Verlet. Temperature comes from equipartition.
Diffraction and melting
Peaks follow Bragg's law for a cubic lattice. Lindemann melting calculates the temperature from the Debye temperature and the constant δ_L.
| Applies to | Formula | Meaning |
|---|---|---|
| Bragg's law | n·λ = 2·d·sin θ | n = 1; for a cubic lattice d = a / √(h² + k² + l²) |
| Thermal expansion | a(T) = a₀·(1 + α·(T − T₀)) | T₀ = 293 K, T from 100 to 1500 K, α from 0.5 to 50·10⁻⁶ per K |
| Lindemann | ⟨u²⟩ = 9·ℏ²·T / (m·k_B·Θ_D²) | melting at √⟨u²⟩ = δ_L · d, d is the nearest-neighbour distance, δ_L is 0.10 by default |
A model checked by calculation and by the printing rules
Checked by calculation, not by a picture
The cell volume is calculated two ways, a dislocation is checked with the Burgers circuit, and dynamics without a thermostat checks the conservation of energy.
Printability follows the rules
The smallest atom and the bond thickness are compared with the FDM minimum wall from the EduFacturing rules core, and the tool suggests a scale.
The tool is for teaching. A shape from a formula is for one central atom with identical ligands, and chains and rings are refused. Dynamics run only on water. A diffraction pattern exists only for cubic lattices, with every basis atom weighted equally, so for compounds such as NaCl real peaks are missing. Lindemann melting is accurate to ±30 to 50%, and the hardness index ranks copper above iron although iron is harder.
Only the Molecule, Lattice and Formula modes give STL and 3MF; the others are analysis with no body to print.
Questions about the 3D molecule model, crystal lattice and printing
How do I find the VSEPR shape of a molecule?
By VSEPR: the shape is determined by the number of ligands X and lone pairs E. One central atom with identical ligands is supported, for example H₂O, CH₄, SO₂, BF₃ and SF₆.
Why is water bent and not linear?
The two lone pairs on oxygen push the bonds closer together, so the angle is 104.45° and not 109.5°. CO₂ has no lone pairs on carbon and is straight.
How many types of crystal lattice does the tool build?
Eight. A crystal lattice is the arrangement of atoms in a crystal, and the tool builds NaCl, CsCl, diamond, zinc blende, copper, iron, magnesium and graphite.
Can I 3D print a molecule model?
Yes, in the Molecule, Lattice and Formula modes. In STL and 3MF every ball and every rod is a closed body at a chosen scale, and the check compares the sizes with the minimum wall.
What does a powder diffraction pattern show?
The peaks in 2θ for a cubic lattice by Bragg's law, with indices (hkl), the d-spacing and a relative intensity. A reflection with a zero structure factor is forbidden and stays out of the table.
How much does Molecules & Crystals cost?
15 EUR a month: Molecules & Crystals is part of Pro. Pro also opens the other Pro tools in the catalog.
The 3D molecule and crystal tool is part of Pro
Pro costs 15 EUR a month and opens all 45 Pro tools.
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Build your molecule
Part of Pro, 15 EUR a month.